`mstyle` attribute defaults

Serve the repo root over HTTP (e.g. python -m http.server 8080) and open http://localhost:8080/mstyle/index.html so ES modules load.

MathML 3 lets mstyle change the default of presentation attributes for its descendants. MathML Core treats mstyle as an mrow and only inherits displaystyle, scriptlevel, mathcolor, mathbackground, mathsize, and dir. mstyle/mstyle.js copies the other attributes onto the elements that accept them (closest mstyle wins; an explicit value on the element wins). The Before column is outside the transform (red outline); the After column is inside .mstyle-after (blue outline).

Before vs after `_MathTransforms.transform`
Description	Before (native)	After (polyfill)
Spec example: `maxsize="50%"` limits both parentheses. Copied onto each `mo`.	$(\frac{a}{b})$	$(\frac{a}{b})$
`linethickness`. Nested `mstyle` wins; an explicit `mfrac` value wins over both. After: medium, then thick, then `1px`.	$\frac{1}{2} \frac{3}{4} \frac{5}{6}$	$\frac{1}{2} \frac{3}{4} \frac{5}{6}$
`width` applies to `mspace` only, not `mpadded`. The empty `mspace` becomes `2em`. The `mpadded` (around the 'z') stays unpadded.	$x y z$	$x y z$
`lspace` applies to `mo` only, not `mpadded`.	$a + b c$	$a + b c$
`align="right"` applies to `munder`, not `mtable`.	$\underset{n}{x+y} \begin{matrix} a & bb \end{matrix}$	$\underset{n}{x+y} \begin{matrix} a & bb \end{matrix}$
`align="left"` applies to `mover`, not `mtable`.	$\overset{n}{x+y} \begin{matrix} a & bb \end{matrix}$	$\overset{n}{x+y} \begin{matrix} a & bb \end{matrix}$
`align="right"` applies to `munderover`, not `mtable`.	${x+y}_{n}^{m} \begin{matrix} a & bb \end{matrix}$	${x+y}_{n}^{m} \begin{matrix} a & bb \end{matrix}$
`rowalign="bottom center top"` and `columnalign="right left center"` apply to `mtable`, not `mtr` or `mtd`.	$\begin{matrix} a + b + c & x & \frac{\frac{y}{1}}{\frac{z}{2}} \\ \frac{\frac{a}{1}}{\frac{b}{2}} & u + v + w & z \\ d & \frac{\frac{e}{1}}{\frac{f}{2}} & p + q + r \end{matrix}$	$\begin{matrix} a + b + c & x & \frac{\frac{y}{1}}{\frac{z}{2}} \\ \frac{\frac{a}{1}}{\frac{b}{2}} & u + v + w & z \\ d & \frac{\frac{e}{1}}{\frac{f}{2}} & p + q + r \end{matrix}$
Attributes consumed by other polyfills: `notation`, `bevelled`, `subscriptshift`.	$x \frac{a}{b} x_{1}$	$x \frac{a}{b} x_{1}$
`scriptsizemultiplier="0.4"` and `scriptminsize="18pt"`. At 64px, the first superscript is ~26pt; the next one stays at least 18pt.	$x^{y^{z}}$	$x^{y^{z}}$
`mathsize="200%"` on `mstyle`. Left on `mstyle`. Not copied onto the enclosed `mi`, `mn`, `mo`, or `mtext`. Should both be the same.	$x 2 + text$	$x 2 + text$
`display="inline"` on `math`, `displaystyle="true"` on `mstyle`. Left on `mstyle`. Not copied onto the enclosed elements. The before/after should be the same.	$\sum_{i = 1}^{n} \frac{a}{b}$	$\sum_{i = 1}^{n} \frac{a}{b}$

mstyle attribute defaults

`mstyle` attribute defaults